A review of persulfate-based advanced oxidation system for decontaminating organic wastewater via non-radical regime

The large amount of refractory organic wastewater produced from industry and agriculture sectors poses a significant threat to both water ecosystems and human health, necessitating the exploration of cost-efficient and efficacious removal techniques. Persulfate, when activated by various catalysts, can produce oxidative species, demonstrating promising potential in remediating organic wastewater. In recent years, numerous studies have unveiled that persulfate can be readily decomposed into nonradicals, which exhibits high selectivity toward pollutants and robust performance in complex wastewater environments. However, the challenges in identifying non-radicals and the unclear catalytic mechanism hinder its further application. This paper critically reviews the research progress on non-radical oxidation in persulfate-based heterogeneous catalytic system. The main advancements and existing challenges in three non-radical oxidation pathways, i.e., singlet oxygen, electron transfer, and high-valent metal oxides, are summarized, and the key factors influencing the production of nonradicals are elaborated. The engineering aspects of non-radical oxidation system are further discussed, and the future prospects of this technology in wastewater treatment are envisaged. This review aims to bridge the knowledge gaps between current research and future requirements.